1. Technical Field
The present invention relates to an optical device, an optical scanner, and an image display device.
2. Related Art
As an optical device used in, for example, a projector, an optical scanner has been known which performs two-dimensional scanning with light (for example, see JP-A-8-322227).
The optical scanner disclosed in JP-A-8-322227 includes an insulating substrate which is provided with a pair of permanent magnets and a scanner body which is supported by the insulating substrate so as to be disposed between the pair of permanent magnets. The scanner body includes a frame-shaped supporting portion, a frame-shaped outer movable plate which is provided inside the supporting portion, and an inner movable plate (mirror) which is provided inside the outer movable plate. The outer movable plate is connected to the supporting portion through a pair of first torsion bars which extend in the X-axis direction and the inner movable plate is connected to the outer movable plate through a second torsion bar which extends in the Y-axis direction perpendicular to the X-axis direction. In addition, coils are provided in the outer movable plate and the inner movable plate.
In the optical scanner having the above-mentioned structure, the interaction between the magnetic field which is generated from each coil by the application of a voltage and the magnetic field generated between a pair of permanent magnets causes the outer movable plate to be rotated about the X-axis together with the inner movable plate, using the first torsion bar as the central axis, and causes the inner movable plate to be rotated about the Y-axis using the second torsion bar as the central axis.
However, in the optical scanner disclosed in JP-A-8-322227, the inner movable plate and the second torsion bar are arranged so as not to overlap each other in a plan view (as viewed from the thickness direction of the inner movable plate). Therefore, the overall dimensions increase depending on the dimensions of the mirror (inner movable plate).
In particular, in the optical scanner disclosed in JP-A-8-322227, for example, when the dimensions of the inner movable plate increases, the second torsion bar needs to be arranged outside in order to respond to the increase in the dimensions. As a result, the dimensions of the outer movable plate increase and the first torsion bar needs to be arranged outside in order to respond to the increase in the dimensions. In addition, when the dimensions of the outer movable plate increase, the mass of the outer movable plate increases. Therefore, the length of the first torsion bar increases and driving force required to rotate the outer movable plate increases.